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Volume 15 Issue 4
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Original Articles
Explicit Expression of Foldy-Wouthuysen Transformation
WANG An-min
Chin. Phys. Lett. 1998, 15 (4): 235-237 .  
Abstract   PDF(pc) (188KB) ( 592 )
The general, explicit and formally closed expression of arbitrary n-times Foldy-Wouthuysen transformations is clearly and strictly derived out. It is proved that if transformed Hamiltonian needs to be approximated to the order 1/mK or mv2K when to involve the orders of the operators, then to make N = [(K + 1)/2]-times Foldy-Wouthuysen transformations is just enough ( “[...]”means to take the part of integer). An example in non-relativistic quantum chromodynamics is given.
Experimental System for Quantum Cryptography Based on Two Nonorthogonal Photon Polarization States
ZHANG Yong, DENG Le, MAO Min, DING Liang-en
Chin. Phys. Lett. 1998, 15 (4): 238-239 .  
Abstract   PDF(pc) (203KB) ( 376 )
Quantum cryptography allows the establishing of a highly confidential sequence of random bits between two parties who share no secret information in advance. Its security is guaranteed by the basic laws of quantum mechanics rather than mathematical difficulty. An experimental system based on a novel protocol for quantum cryptography using only two nonorthogonal photon polarization states is implemented. The photon sources are two semiconductor laser diodes operated at 680 nm, their light pulses which are heavily attenuated to far below one photon per pulse are employed to encode the key. Gated single photon detection technique is used to minimize the dark count effect of the photon multiplier tube. Key establishing rate of 40 b/s and error rate of 2.1 % are obtained. Compared with other systems, our system has the simplest experimental setup.
Thermodynamical and Statistical-Mechanical Entropies of the General Static Spherically Symmetric Black Hole
JING Ji-liang
Chin. Phys. Lett. 1998, 15 (4): 240-242 .  
Abstract   PDF(pc) (223KB) ( 507 )
The thermodynamical entropy of the general four-dimensional static spherically symmetric black hole is obtained by using the Euclidean path integral approach of Gibbons-Hawking, and its statistical-mechanical entropy is calculated according to the brick wall model of ’t Hooft. It is shown that the two entropies are not identical in general and the difference between them depends on the area of the horizon and the Ricci scalar curvature on the event horizon.
Reentrant Transitions Induced by Correlation Between Colored Noises
ZHOU Xiao-ji, CAO Li, WU Da-jin,
Chin. Phys. Lett. 1998, 15 (4): 243-245 .  
Abstract   PDF(pc) (185KB) ( 353 )
In the study, a bistable system is driven by additive colored noise and multiplicative colored noise, whose correlation is of an exponential farm. When the noises are correlated, it is found that the system undergoes a reentrant transition as the correlation strength between noises or multiplicative noise intensity changes, while there is no such phenomenon as the additive noise intensity or the time of correlation changes. No reentrant transition exists when the noises are uncorrelated.
Scaling Properties of the Period-Adding Sequences in a Multiple Devil’s Staircase
WU Cai-yun, QU Shi-xian, WU Shun-guang, HE Da-ren,
Chin. Phys. Lett. 1998, 15 (4): 246-248 .  
Abstract   PDF(pc) (193KB) ( 377 )
In this letter the scaling properties of the period-adding sequences in a so-called “multiple Devil’s staircase” are reported. It is certified both analytically and numerically that the width of the i-th phase-locked plateau in a sequence scales as In |Δe(i)| ∝ i, and the position of the plateau scales as In |e -ei| ∝ i. These properties are qualitatively different from those of the period-adding sequences in conventional Devil’s staircases.
Nonlinear Control of Chaos
LIU Ren-hong, TAN Wei-han
Chin. Phys. Lett. 1998, 15 (4): 249-251 .  
Abstract   PDF(pc) (189KB) ( 471 )
The nonlinear and the exact control of chaos is deduced. Using these methods we achieve a simultaneous and instantaneous control of the scheduled unstable 2kp points for the logistic and the Henon map. The derivatives needed in the nonlinear method have been evaluated experimentally from the time series xn, without the pre-knowledge of the function f(x). The difficulty confronted in the optimum control may be overcome by introducing the nonlinear control.
Description of the Hexadecapole Deformation Parameter in the sdg Interacting Boson Model
LIU Yu-xin, SUN Di, WANG Jia-jun, HAN Qi-zhi
Chin. Phys. Lett. 1998, 15 (4): 252-254 .  
Abstract   PDF(pc) (250KB) ( 371 )
The hexadecapole deformation parameter β4 of the rare-earth and actinide nuclei is investigated in the framework of the sdg interacing boson model. An explicit relation between the geometric hexadecapole deformation parameter β4 and the intrinsic deformation parameters ε4 , ε2 are obtained. The deformation parameters β4 of the rare-earths and actinides are determined without any free parameter. The calculated results agree with experimental data well. It also shows that the SU(5) limit of the sdg interacting boson model can describe the β4 systematics as well as the SU(3) limit.

Non-equilibrated Emission of Intermediate Mass Fragments in 25 MeV/n 40Ar+natAg Reaction
QIAN Tao, JIANG Dong-xing, HUA Hui, JIN Gen-ming, WU En-jiu, ZHENG Ji-wen, YIN Shu-zhi, TAN Ji-lian, HE Zhi-yong, LI Zu-yu, DUAN Li-min
Chin. Phys. Lett. 1998, 15 (4): 255-257 .  
Abstract   PDF(pc) (216KB) ( 451 )
In order to clarify whether statistical or dynamical treatments for emission of intermediate mass fragments (IMFs) will be needed in the intermediate energy heavy ion collisions, the measured angular and energy distributions of IMF (3≤ Z ≤6 ) in 25 MeV/n 40Ar+natAg were analyzed by means of statistical calculation code GEMINI and quantum molecular dynamics code (QMD). While the angular distribution calculations with GEMINI code are not compatible with the experimental ones, the QMD calculations for inclusive angular distributions and energy spectra of IMF are in good agreement with the measured ones.
Exact Treatment for Two Ultracold Ions in a Two-Dimensional Penning Trap
FENG Mang, FANG Xi-ming, SHI Lei, YAN Min, ZHU Xi-wen
Chin. Phys. Lett. 1998, 15 (4): 258-259 .  
Abstract   PDF(pc) (154KB) ( 322 )
The Schrödinger equation of two ultracold ions confined in xy plane of the Penning trap is exactly solved and the analytical form of the wave function of the system is obtained. A numerical calculation for a continued fraction presents the relation among the beigenenergies, the Coulomb interaction and the azimuthal number.
Vibrational Spectrum of Methane in an Algebraic Model
HOU Xi-wen, DONG Shi-hai, MA Zhong-qi
Chin. Phys. Lett. 1998, 15 (4): 260-262 .  
Abstract   PDF(pc) (191KB) ( 421 )
A U(2) algebraic model is used to explain the stretching and bending vibrational spectrum of methane, where the interactions between the stretching and the bending modes are taken into account. This model provides good fits to the experimental vibrational eigenvalues with the smaller standard deviations of 9.57 and 9.08 cm-1 than those in other published algebraic models.
Channel Dependence of Dielectronic Recombination Rate Coefficients of Fe25+ Ion
DONG Chen-zhong, WANG Jian-guo, QU Yi-zhi
Chin. Phys. Lett. 1998, 15 (4): 263-265 .  
Abstract   PDF(pc) (182KB) ( 351 )
In the frame of quantum defect theory, the state-testate dielectronic recombination rate coefficients of Fe25+ ion are calculated by a simple relativistic configuration interaction method. The calculated results are further expressed with a two-parameter fitting formula, and then the dependence of fitting parameters on radiative decay final channel is studied.

Effects of a Novel Drift Term Due to Cross Correlation Between Additive and Multiplicative Noises in a Single-Mode Laser
LONG Quan, CAO Li, WU Da-jin, LI Zai-guang
Chin. Phys. Lett. 1998, 15 (4): 266-268 .  
Abstract   PDF(pc) (225KB) ( 345 )
It is found that a novel drift term, purely induced by cross correlation between multiplicative and additive noises, in the one-dimensional Langevin equation for a single-mode laser intensity has a significant effect on the intensity statistical properties near and below threshold, and when colored multiplicative noise is involved. This term makes the laser intensity fluctuations lower but effective eigenvalues larger for positive noise cross correlation.
Two- and Three-P hoton Resonant Third Harmonic Generation in Molecular Nitrogen
WANG Peng-qian, CAO Chuan-shun, XIE Xiao-bo, SUN Tao-heng
Chin. Phys. Lett. 1998, 15 (4): 269-271 .  
Abstract   PDF(pc) (207KB) ( 368 )
Tunalbe coherent extreme ultraviolet radiation has been produced in nitrogen by third harmonic generation (THG) processes enhanced by two-photon resonance with the a1IIg(v' = 1) state and three-photon resonance with the c'4 1Σ+u(v' = 1) state, respectively. The highly resolved THG spectra imply that THG can be used to probe the higher excited states and to detect the rotational population of a molecular gas.
Characterization of Clusters in a Novel Nd3+-Doped Polymer Optical Fiber
YANG Bao, MING Hai, ZHANG Qi-jin, XIE Jian-ping
Chin. Phys. Lett. 1998, 15 (4): 272-274 .  
Abstract   PDF(pc) (197KB) ( 513 )
A step index-type Nd3+-doped polymer optical fiber (POF) was prepared by using bulk polymerization of solution of Nd3+-octanoate (NOA) and methyl and methacrylate. A method of wide-angle x-ray diffraction was used to measure the solubility of NOA. In a high concentration Nd3+ doped POF, a residual absorption at 810nm could not be saturated, which is attributed to the high clustered ion rate in the Nd3+ POF. A model based on the rate equations to infer the clustered ion rate by the measurement of transmission is presented.

Synchronous Spatiotemporal Oscillation Between Two Parametrically Excited Bound States
WANG Xin-long, WEI Rong-jue
Chin. Phys. Lett. 1998, 15 (4): 275-277 .  
Abstract   PDF(pc) (257KB) ( 433 )
The bound state is one of the elemental localized excitations in a parametrically driven systems. In the molecule-like structure, the two identical solitons can interact with each other as a classic “oscillator”. Here the dynamics of two interacting bound states is explored by both experiment and computation. The experiment reveals several important dynamical features, in particular, the polarity ordering rule that determines the stability of a compound structure, and the synchronization in the coupling pairs of opposite polarity which leads to a symmetric and harmonic spatiotemporal oscillation. All these interesting phenomena are numerically simulated with the parametrically driven, damped nonlinear Schröding equation, and their nonlinear dynamics is further concluded as a stability diagram in parameter space.
New Method for Solving Elasticity Problems of Some Planar Quasicrystals and Solutions
LI Xian-fang, FAN Tian-you
Chin. Phys. Lett. 1998, 15 (4): 278-280 .  
Abstract   PDF(pc) (178KB) ( 609 )
A new method for solving elasticity problems of some planar quasicrystals is presented. The set of partial differential equations for the phonon and phason displacement components is reduced to a single higher-order equation by introducing a displacement function. A general solution formulation is suggested. As an example, the elastic field caused by a dislocation in planar quasicrystals of point groups 5 m , 10, and 10mm is calculated.
Phenomenological Studies on Internal Friction of Noncrystalline Materials in Structural Relaxation Processes
CAI Jian-le, QIAO Chu-liang
Chin. Phys. Lett. 1998, 15 (4): 281-283 .  
Abstract   PDF(pc) (164KB) ( 366 )
Based on not only the ideas of phenomenological investigations about the internal friction of crystalline materials but also the studies on the internal friction laws of noncrystalline materials during structural relaxation processes in recent years, the method of making relaxation cell is put out. In the method, traditional mechanics parameter model and two-level model are unified, so phenomenological studies on the internal friction of noncrystalline materials during structural relaxation processes are made and a new relaxation law is formed.
Studies on CsBr with Synchrotron Radiation Under Ultrahigh Pressure up to 115GPa
WANG Li-jun, CHEN Liang-chen, LI Feng-ying, GU Hui-cheng, ZHOU Lei, CHE Rong-zheng
Chin. Phys. Lett. 1998, 15 (4): 284-286 .  
Abstract   PDF(pc) (164KB) ( 473 )
In situ high pressure energy dispersive x-ray diffraction experiments have been carried out on CsBr by using diamond anvil cell device with synchrotron radiation source. The maximum pressure is 115 GPa. The structure of CsBr is changed from simple cubic phase to tetragonal phase at pressure about 53 GPa, marked by the splitting of its strongest diffraction line (110). At pressure above 98GPa, the color change of CsBr from transparent to red-brown was observed. No pressure-induced transition from insulator to metal is found at higher pressure up to 115GPa.
Interaction Potentials and Equation of State of Solid Deuterium: a Path Integral Monte Carlo Study
CUI Tian, ZOU Guang-tian, K. B. Whaley*
Chin. Phys. Lett. 1998, 15 (4): 287-289 .  
Abstract   PDF(pc) (227KB) ( 403 )
Within a movable and orientable rigid rotor model, four interaction potentials of solid deuterium (hydrogen) system from combinations of two isotropic and two anistropic parts are tested by the path integral Monte Carlo method in a constant-pressure ensemble. With the best one of the potentials, the equation of state of deuterium is quantitatively in agreement with the experimental data. For understanding the quantum nature of the solid, the energies of the system at different temperatures are also calculated, the results show strong zero-point motions exist in the solid. As would be expected, the quantum corrections to both the rotational and the translational kinetic energies decrease with increasing temperature, and increase with pressure.
Nucleation and Growth Characteristics of Metal Films on C60(111) Surface
XU Wen-tao, LI Xiang, WANG Hai-qian, YANG Li, WU Zi-qin, HOU Jian-guo
Chin. Phys. Lett. 1998, 15 (4): 290-292 .  
Abstract   PDF(pc) (589KB) ( 406 )
C60 single crystals oriented at [111] about 1 μm in size, were grown in C60 film on NaCl (001) substrate. Bilayer films of nickel, gold, silver, and indium over C60 on NaCl substrate prepared by vacuum deposition method were studied with a transmission electron microscope. It was found that for different kinds of metals, their nucleation and growth characteristics on C60 (111) surface are quite different. This phenomenon is mainly attributed to different activation energies of the four metals. Analyses of the experimental results indicate that the activation energies of Ni, Au, Ag, and In adatoms on C60(111) surface change in a descent order.

Vertical Transport in GaAs/AlAs Superlattice with Weak Coupling Between Wells
HE Li-xiong, SUN Bao-quan, WU Jian-qing
Chin. Phys. Lett. 1998, 15 (4): 293-295 .  
Abstract   PDF(pc) (250KB) ( 438 )
Vertical transport I-V relations of type-I GaAs/A1As superlattices with doped wells and weak coupling between wells at 77K were investigated with quasistatic and dynamic method. Spontaneous current oscillations are also investigated. The domain formation time 70 ± 30 ns is directly measured. By using discrete-tunneling model, the key parameters of the relation between tunneling current and the bias between adjacent wells were quantitatively determined from the experimental data.
Magnetoresistance and Interlayer Exchange Coupling in Ferromagnetic/Nonmagnetic/Insulator (Semiconductor) /Ferromagnetic Tunnel Junctions
ZHANG Wu-shou, LI Bo-zang
Chin. Phys. Lett. 1998, 15 (4): 296-298 .  
Abstract   PDF(pc) (230KB) ( 313 )
Based on the two-band model and free-electron approximation, a treatment of the magnetoresistance (MR) and interlayer exchange coupling (IEC) for ferromagnetic/nonmagnetic/insulator (semiconductor)/ferromagnetic tunnel junctions is presented. It is found that properties of the junctions are intermediate between tunnel junctions and metallic magnetic multilayers. The MR and IEC are all the oscillatory functions of the thickness of nonmagnetic layer. The results have potential in designing spin-polarized tunneling devices with large field-sensitivity.

Raman Scattering of Znl-xCdxSe/ZnSe Strained Superlattices Under Hydrostatic Pressure
CHI Yuan-bin, WANG Li-zhong, LI Yan-mei, ZOU Guang-tian, LI Wen-sen, FAN Xi-wu, YANG Bao-jun
Chin. Phys. Lett. 1998, 15 (4): 299-301 .  
Abstract   PDF(pc) (228KB) ( 368 )
The Raman scattering in Zn0.74Cd0.26Se/ZnSe superlattices under hydrostatic pressures up to 4.53 GPa at room temperature has been studied. The pressure-dependences of the ZnSe-like LO-phonon (LOb) and the Zn0.74Cd0.26Se-like LO-phonon (LOw) have been obtained. At 2.7GPa, the pressure-coefficients of both LOb and LOw phonon energies increase abruptly The 2LOw-phonon resonance has been observed at 1.82GPa with 488.0nm excitation for the Zn0.75Cd0.25Se/ZnSe superlattices.
Photoluminescent Properties and Applications of Platinum(lI) Complexes Molecularly Dispersed in Polymer Matrices
MA Yu-guang, SHEN Jia-cong, Biing-Chiau Tzeng, Chi-Ming Che
Chin. Phys. Lett. 1998, 15 (4): 302-304 .  
Abstract   PDF(pc) (181KB) ( 414 )
The photoluminescence of some platinum (II) complexes of aromatic α-diimines and pyridine-2-thiolates is enhanced upon incorporation into the polymer matrices polymethmethylacrylate (PMMA), polycarbonate, and polystyrene. Some applications of the platinum (II)-PMMA films as luminscent sensors reported. When platinum (II)-PMMA films are in ethanol solutions with different chloroform concentration, there is a systematic decrease of emission intensity with increasing chloroform concentration and the variation follows a Stern-volmer relationship.
Gamma-Ray Irradiation Effects on Electroluminescence from Au/Extra Thin Si-Rich SiO2 Film/p-Si Structures
LI An-ping, ZHANG Bo-rui, QIAO Yong-ping, QIN Guo-gang, MA Zhen-chang, ZONG Wan-hua
Chin. Phys. Lett. 1998, 15 (4): 305-307 .  
Abstract   PDF(pc) (168KB) ( 342 )
We have studied the effects of γ-ray irradiation on electroluminescence (EL) from Au/extra thin Si-rich SiO2 film/p-Si Structures. After γ-ray irradiation, for the structure with a 600°C annealed Si-rich SiO2 film a new blue EL band with a peak at around 480nm was observed, and for the structure with a 300°C annealed Si-rich SiO2 film the red EL band shifts from 670 to 660nm and its intensity and full width at half maximum increase pronouncedly. The experimental results demonstrate that the defects induced by γ-ray irradiation are responsible for the blue EL band as well as for the variations of the red EL band.
Effect of Solvents on the Absorption Properties of GaP Nanocrystals
CUI De-liang, GAO Shan-min, HUANG Bai-biao, YU Shu-qin, QIN Xiao-yan, JIANG Min-hua
Chin. Phys. Lett. 1998, 15 (4): 307-309 .  
Abstract   PDF(pc) (368KB) ( 354 )
GaP nanocrystals were synthesized by both the organic solvent reflux and high temperature high pressure benzene thermal synthesis methods. The effect of organic solvent on the optical absorption properties of GaP nanocrystals were studied. The results show that crystal grains of the sample synthesized by the latter method have better quality and uniformity. The solvents which consist of polar molecules and form strong chemical bonds with Ga atoms cause obvious redshift of the absorption spectra of GaP nanocrystals. The absorption spectra redshift much more if the solvent molecules have π electrons which involved in the formation of complex bond between Ga atoms and solvent molecules.
Outflows of Massive Stars in Cluster
MAO Xin-jie, QIU Hong-mei, WANG Yu-chun
Chin. Phys. Lett. 1998, 15 (4): 310-312 .  
Abstract   PDF(pc) (221KB) ( 313 )
Massive stars often tend to be in cluster when they form in molecular clouds, and bipolar molecular outflows occur during the forming process of stars. On the basis of newly observed bipolar molecular outflows associated with massive stars, three properties are proposed to statistically identify massive stars whether in cluster or not as the driving engines of the flows. For clustering massive stars with some exceptions, their outflow collimation factors are generally poor and less than two, and the correlations of the flow momentum rate and the mass flow rate with the central source bolometric luminosity deviate the ones for selected well-resolved 16 flows.

27 articles